Multi-Period Discrete-Time Repetitive Control for Permanent Magnet Linear Synchronous Motor

While tracking the periodic input signal, the position-dependent periodic thrust ripple caused by ending effect, load disturbance and the friction of the permanent magnet linear synchronous motor (PMLSM) will reduce the servo performance of the system. Especially when the periods of the reference input signal and thrust fluctuation interference signal are not synchronous, the precision of periodic signal tracked by the servo system is reduced, which lead to the reduction of the servo system’s periodic signal tracking precision. Therefore, a multi-period discrete repetitive controller using two improved prototype repetitive controllers which are incomplete parallel to restrain\track the multi-period input signal was designed. Theoretical analysis and simulation results show that the proposed scheme can improve the precision of the system tracking periodic signals and restrain the periodic thrust fluctuations effectively.